<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script src="js/vue.js"></script>
</head>
<body>
    <div id="app">
        <p v-if="grade>=60">合格</p>
        <p v-else>不合格</p>
        <hr>
        等级：
        <p v-if="grade < 60">差</p>
        <p v-else-if="grade >= 60 && grade < 80">中</p>
        <p v-else-if="grade >= 80 && grade < 90">良</p>
        <p v-else>优</p>
    </div>

    <script>
        var vueObj = new Vue({
            el:"#app",
            data:{
                grade:60
            }
        });
    </script>

</body>
</html>